Position based personal digital assistant

ABSTRACT

A task description is stored in a database accessible by a mobile computer system. The mobile computer system receives positioning information corresponding to its geographic location and indexes the database based on the positioning information when the information indicates that the mobile computer system is in a geographic location that facilitates completion of a task associated with the task description. The database may be resident in the mobile computer system or accessible in other ways, for example, via the Internet. The task description preferably includes a geocode which corresponds to the geographic location at which completion of the task may be facilitated. The task description may also include textual, voice or other message which can be displayed and/or played back to a user. The positioning information may be obtained from a GPS satellite, a GLONASS satellite or a pseudolite. The mobile computer system may be a portable unit, such as a PDA, or integrated within a vehicle.

RELATED APPLICATION

This application is a Continuation of application Ser. No. 08/738,938filed Oct. 24, 1996, now U.S. Pat. No. 5,938,721 issued Aug. 17, 1999.

FIELD OF THE INVENTION

The present invention relates generally to real time positioning systemsand, more particularly, to the use of such systems to control access tocomputer databases to assist in task scheduling.

BACKGROUND

Personal Digital Assistants (PDAs) have become more and more common intoday's society. The term PDA refers generally to mobile computersystems, typically handheld, which users employ for a variety of taskssuch as storing telephone and address lists (databases), calendaringinformation, task (i.e., to-do) lists, etc. Some PDAs also incorporate awireless communication link, allowing the unit to operate as a portablefacsimile device, Internet access device and/or pager. Further, PDAs canbe configured to operate with Global Positioning System (GPS) receiversas described in U.S. Pat. No. 5,528,248 to Steiner et al., entitled“Personal Digital Location Assistant Including a Memory Cartridge, A GPSSmart Antenna and a Personal Computing Device” assigned to the assigneeof the present invention and incorporated by reference herein.

The GPS utilizes signals transmitted by a number of in-view satellitesto determine the location of a GPS antenna which is connected to areceiver. Each GPS satellite transmits two coded L-band carrier signalswhich enable some compensation for propagation delays through theionosphere. Each GPS receiver contains an almanac of data describing thesatellite orbits and uses ephemeris corrections transmitted by thesatellites themselves. Satellite to antenna distances may be deducedfrom time code or carrier phase differences determined by comparing thereceived signals with locally generated receiver signals. Thesedistances are then used to determine antenna position. Only thosesatellites which are sufficiently above the horizon can contribute to aposition measurement, the accuracy of which depends on various factorsincluding the geometrical arrangement of the satellites at the time whenthe distances are determined.

Distances measured from an antenna to four or more satellites enable theantenna position to be calculated with reference to the global ellipsoidWGS-84. Local northing, easting and elevation coordinates can then bedetermined by applying appropriate datum transformation and mapprojection. By using carrier phase differences in any one of severalknown techniques, the antenna coordinates can be determined to anaccuracy on the order of ±1 cm.

Although U.S. Pat. No. 5,528,248 describes how a GPS receiver can beintegrated with a PDA to display navigation information for a user, itdoes not describe how positioning information provided to the PDA can beused in other ways.

SUMMARY OF THE INVENTION

According to one embodiment, a computer assisted method of schedulingtasks is provided. The method allows a task description to be stored ina database accessible by a mobile computer system. The mobile computersystem receives positioning information corresponding to its geographiclocation and indexes the database based on the positioning informationwhen the information indicates that the mobile computer system is in ageographic location that facilitates completion of a task associatedwith the task description.

The database may be resident in the mobile computer system or accessiblein other ways, for example, via the Internet. The task descriptionpreferably includes a geocode which corresponds to the geographiclocation at which completion of the task may be facilitated. The taskdescription may also include textual, voice or other messages which canbe displayed and/or played back to a user. The positioning informationmay be obtained from a GPS satellite, a GLONASS satellite or apseudolite. The mobile computer system may be a portable unit, such as aPDA, or integrated within a vehicle.

A second embodiment provides a computer assisted method of using ageocoded database. In this embodiment, a mobile computer system istransported to a first location having first geographic coordinates at afirst time. At the first location, RF signals which contain informationindicative of the location of a source of their transmission arereceived and processed to derive the geographic coordinates of the firstlocation. The geographic coordinates of the first location areassociated with a descriptor indicative of the first location in adatabase associated with the mobile computer system so as to form ageocoded entry in the database and a task to be accomplished at thefirst location is similarly associated with the geocoded entry in thedatabase.

The mobile computer system is transported to a second location at asecond time and RF signals containing information indicative of thesource of the signals are received and processed to determine thegeographic coordinates of the second location. The geographiccoordinates of the second location are analyzed to determine whether thesecond location is within a predetermined range of the first locationand, if so, a user is alerted. The user may be alerted by displaying analert message, such as a task description corresponding to the task tobe accomplished at the first location, on a display associated with themobile computer system.

A further embodiment provides a mobile computer system having a locationdetermination unit configured to receive and process RF signalscontaining information indicative of the location of a source of thesignals, a database coupled to the location determination unit andincluding location coordinates indicative of a location of interest anda database interface unit configured to access the database according tothe location of the mobile computer system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which:

FIG. 1 illustrates a digital system configured with a mobile computersystem, a location determination unit and a database according to oneembodiment; and

FIG. 2 illustrates a vehicle configured in accordance with the presentinvention located near a pick-up location.

DETAILED DESCRIPTION

The following description of a position based personal digital assistantsets forth numerous specific details in order to provide a thoroughunderstanding of the present invention. However, after reviewing thisspecification, it will be apparent to those skilled in the art that thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known structures, programmingtechniques and devices have not been described in detail in order not tounnecessarily obscure the present invention.

Some portions of the detailed description which follows are presented interms of operations on data within a computer memory. These descriptionsare the means used by those skilled in the relevant arts to mosteffectively convey the substance of their work to others skilled in theart. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared and otherwise manipulated. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers or the like. It should be borne in mind, however, that all ofthese and similar terms are to be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities. Unless specifically stated otherwise, it will be appreciatedthat throughout the description of the present invention, use of termssuch as “processing”, “computing”, “calculating”, “determining”,“displaying” or the like, refer to the action and processes of acomputer system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (electronic)quantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

Referring to the accompanying Figure, a digital system 5 having adatabase 10, a mobile computer system 20 and a location determinationunit 30 is shown. Database 10 may be a separate database maintained atsome location remote from mobile computer system 20 or it may be a localdatabase maintained within mobile computer system 20. Mobile computersystem 20 may be a personal digital assistant or other mobile computersystem (e.g., a notebook or other personal computer) or it may be anintegrated computer system within a vehicle. Location determination unit30 may be a Global Positioning System (GPS) receiver of other unitcapable of determining a geographic location of an accompanying antenna32.

It should be appreciated that although database 10, mobile computersystem 20 and location determination unit 30 are illustrated as distinctunits, in some embodiments these items may comprise a single unit, suchas a personal digital assistant or notebook computer. In suchembodiments, location determination unit 30 may be housed within a card(PC Card) compatible with the Personal Computer Memory CardInternational Association PC Card Standard, release 2.0, published bythe Personal Computer Memory Card Interface Association (PCMCIA),September 1991. In other embodiments, location determination unit 30 maycomprise a GPS Smart Antenna or other GPS receiver.

In yet other embodiments, elements of digital system 5 may form anintegrated system within a vehicle, aircraft, boat or other mobile unitand database 10 may be stored within a memory device housed in a PC Cardor on another transportable computer readable media such as a disk or CDROM. Database 10 is preferably a geocoded database and will be describedin further detail below. In some cases, mobile computer system 20 mayshare some circuitry with location determination unit 30. For example,the two units may share a digital signal processor or othermicroprocessor which performs the computations required to derive thegeographic location of the digital system 5 (i.e., antenna 32) usingsignals transmitted by GPS satellites or other sources (e.g., GLONASSsatellites and/or pseudolites).

Mobile computer system 20 typically includes a microprocessor 21 and asystem bus 22. Microprocessor 21 is coupled to system bus 22, allowingmicroprocessor 21 to communicate with the other elements which make upmobile computer system 20, location determination unit 30 and database10. Mobile computer system 20 may also include a ROM 23 which typicallystores computer readable instructions to be executed by microprocessor21 upon power up. Such instructions may further include an operatingsystem for mobile computer system 20 where such an operating system isnot stored within another nonvolatile memory. Mobile computer system 20may further include a memory (Mem) 24 which may be a volatile memory(i.e., a random access memory or RAM) for use during periods when mobilecomputer system 20 is powered up. The Mem 24 may also include a harddisk or other long term, nonvolatile memory for storage of applicationprograms and/or data when mobile computer system 20 is not powered up.In other cases, these application programs may be stored in ROM 23. ROM23 and Mem 24 are typically coupled to system bus 22 to allow access bymicroprocessor 21. In some embodiments, ROM 23 and Mem 24 may be coupledto microprocessor 21 over a separate memory bus (not shown).

To facilitate use of mobile computer system 20 by an operator, userinterface 25 and display 26 are provided and each are coupled to systembus 22. User interface 25 may include a familiar keyboard and mouse (orother pointing device such as a pen). In addition, some mobile computersystems 20 may have a voice synthesizer included as part of userinterface 25 to allow activation of various functions by voice command.In other embodiments, the user interface 25 may be a touch sensitivescreen which also forms part of a visual display 26. Other userinterfaces may also be used. Display 26 may be a visual display such asa liquid crystal display screen, or other screen. In other embodiments,display 26 will include alert lights, such as those commonly found onautomobile dashboards. Where mobile computer system 20 is integratedwithin a vehicle, display 26 may form part of a heads up display ordashboard display within the vehicle. When display 26 forms part of aheads up display, the heads up display may provide information such asthe vehicle's current speed and location (e.g., latitude and longitude).The heads up display may further include an area for displaying textmessages, such as the task description stored in database 10.Alternatively, the heads up display may only provide an alert indication(such as an icon or an alert symbol, etc.). Such a heads up display maybe displayed on an appropriate section of the vehicle's windshield, suchas a corner of the windshield near the driver's position or directlyabove the steering wheel, so as to allow for easy use by the driverwithout obstructing the driver's view of the road. Display 26 may alsoinclude a voice synthesizer (optionally shared with user interface 25)and speaker system to allow for playback of voice messages. Thisarrangement may allow for voice messages to be played back through thevehicle's existing sound system (e.g., an AM/FM stereo system). Otherdisplays may also be used.

Mobile computer system 20 also includes interface 27 which allows mobilecomputer system 20 to communicate with location determination unit 30.Interface 27 provides an electrical connection between mobile computersystem 20 and location determination unit 30 and may correspond to anRS-232 or RS-422 interface. In some embodiments, where locationdetermination unit 30 comprises a GPS server located as a unit on avehicle bus system, interface 27 allows for proper electrical couplingbetween mobile computer system 20 and a vehicle communication bus. Assuch, interface 27 will be configured according to the protocol formessage exchange across the bus.

A communications bus is useful for delivering data and other electronicsignals from one device to another in a vehicle. Without use of such abus, as the number of vehicle devices increases, duplication of vehiclesensors and increasing use of point-to-point wiring between devices isrequired, which can result in large and needlessly complex wiring looms.Use of such a bus allows use of unduplicated vehicle sensors andminimizes use of point-to-point wiring, by making all measurements andsignals available simultaneously to all devices that are connected bythe bus. Several standards for such vehicle bus systems exist, forexample, the J1587 and J1708 specifications for bus systems published bythe Society of Automotive Engineers and the standards for communicationbuses as set forth by the Society of Automotive Engineers and ControllerArea Network (CAN) as documented in ISO 11893:1993, for high speedapplications, and in ISO 11519.1:1994—ISO 11519.4:1994, for low speedapplications, all of which are incorporated herein by reference.

The J1587 (issued as 1988-01 and in revised form as 1994-01-10 and laterrevisions) and J1708 (issued as 1986-01 and in revised form as1990-10-05 and later revisions) specifications recite standards anddefine signal formats for use of microcomputer systems in heavy dutyvehicle applications, such as provision of electronic data on vehicleand component performance, vehicle routing and scheduling, vehicledriver information and vehicle cargo reformation. Each signal that istransmitted using a signal bus complying with these standards includes:(1) a message identification (MID) number (three digits from 0-255, withMIDs 0-127 being defined in J1708 and MIDs 128-255 defined in J1587);(2) one or more measured parameter values associated with and identifiedby the MID; and (3) a check sum. Parameter update time intervals andpriorities for transaction of different groups of MIDs are currentlybeing developed.

The user segment components of a GPS system carried on a vehicle areconnected using a communications bus in the same manner as are otherdevices on the bus. An electrical connection between the server and thebus is made using interface circuitry that complies with applicablestandards. Inexpensive interface ICs are readily available for busesthat conform to the CAN standards.

Typically, each device that is part of a GPS user segment on a vehiclewill have a unique bus address. GPS data can be provided or delivered intwo ways. First, a GPS user segment device (such as locationdetermination unit 30) can provide vehicle location, vehicle velocityand/or absolute or local time information for use on the vehicle, usingpackets that identify the source and destination(s) addresses of suchdata on the bus and that identify the type of data (location, velocity,time, etc.) contained in the packet.

Second, the GPS data can be provided at a central server, and any device(such as mobile computer system 20) requiring such data can address adata request to the GPS server. The server then packages the requesteddata in a packet, frame or other suitable format and sends the packageddata directly to the requesting device, using the bus. This approach maybe more flexible in that it (1) allows a client to request and promptlyreceive GPS data and non-GPS data, (2) allows data to be requested andreceived only when such data is needed, rather than transporting alldata on the bus as soon as such data is available, regardless of need,and (3) provides such data in more convenient formats for individualclient use. Related GPS data may include GPS receiver health, GPSreceiver correction status, vehicle tracking status and other similarinformation. Information can also be provided to, and stored on, theserver to improve or correct the GPS receiver performance. Suchinformation may include real time clock information, to reduce the timerequired for initial acquisition or reacquisition of GPS satellitesignals, and may include DGPS correction data to improve the accuracy ofreal time determination of vehicle present location. Such DGPScorrection data may be obtained from a variety of commercial or othersources using well-known radio-based communications links such as FMsubcarriers, private or packet radio links to private servers or serversaccessed through the Internet or other cellular phone links.

Location determination unit 30 has an associated antenna 32 forreceiving signals from GPS satellites and/or other sources of GPSsignals (e.g., pseudolites, FM subcarriers, etc.) Antenna 32 providesthe received signals to Receiver (Rx) Front-end 34 where the signals aredownconverted and often digitized for further processing by GPSProcessor 36.

The manner in which GPS processing is accomplished is well known in theart. Briefly, GPS receivers normally determine their position bycomputing relative times of arrival of signals transmittedsimultaneously from a multiplicity of GPS satellites. These satellitestransmit, as part of their message, both satellite positioning data aswell as data on satellite clock timing and “ephemeris” data for eachsatellite. Using this data, the GPS receiver computes pseudoranges whichare simply the time delays measured between the received signal fromeach satellite and a local clock.

Many GPS receivers utilize correlation methods to compute pseudoranges.GPS signals contain high rate repetitive signals called pseudorandom(PN) sequences. The codes available for civilian applications are calledC/A codes, and have a binary phase-reversal rate, or “chipping” rate, of1.023 MHz and a repetition period of 1023 chips for a code period of 1msec. The code sequences belong to a family known as Gold codes. EachGPS satellite broadcasts a signal with a unique Gold code. For a signalreceived from a given GPS satellite, following the downconversionprocess to baseband, a correlation receiver multiplies the receivedsignal by a stored replica of the appropriate Gold code contained withinits local memory, and then integrates, or lowpass filters, the productin order to obtain an indication of the presence of the signal. Thisprocess is termed a “correlation” operation. By sequentially adjustingthe relative timing of this stored replica relative to the receivedsignal, and observing the correlation output, the receiver can determinethe time delay between the received signal and a local clock. Theinitial determination of the presence of such an output is termed“acquisition.” Once acquisition occurs, the process enters the“tracking” phase in which the timing of the local reference is adjustedin small amounts in order to maintain a high correlation output. Thecorrelation output during the tracking phase may be viewed as the GPSsignal with the pseudorandom code removed, or, in common terminology,“despread.” This signal is narrow band, with bandwidth commensurate witha 50 bit per second binary phase shift keyed data signal which issuperimposed on the GPS waveform.

The above operations are performed by GPS processor 36 (or by a commonprocessor such as microprocessor 21 where location determination unit 30and mobile computer system 20 share such circuitry) and may be achievedin dedicated hardware or software. The output will be the geographiccoordinates (e.g., latitude, longitude and altitude) of the antenna 32.It is assumed here that antenna 32 is positioned such that there is noappreciable difference between its geographic coordinates and those ofmobile computer system 20. Also, the positioning information provided bylocation determination unit 30 may be enhanced through the use of DGPStechniques as is common in the art.

The output of GPS processor 36 is communicated to mobile computer system20 via interface 38. Interface 38 may be an RS-232 or RS-422 interface.Alternatively, where location determination unit 30 operates as a GPSserver, providing location information to a variety of systems within avehicle, interface 38 will be configured to provide appropriateelectrical coupling to a bus interconnecting the various vehiclesystems.

As mentioned above, database 10 is preferably a geocoded database. Thisterm is best understood with reference to the manner in which digitalsystem 5 is used by an operator. Typically, mobile computer system 20will store various application programs, including a scheduling programwhich allows an operator to store reminders in the form of “To-Do” listsor other forms. Such scheduling programs are common in the art and oftenallow the user to prioritize tasks to be accomplished according to avariety of criteria, including due dates, etc. The present inventionprovides a means by which tasks can be scheduled and/or prioritizedbased on location. Tasks are assigned using a task descriptor (e.g., atext and/or voice message describing the task) and stored in database10. Typically, the task descriptor will include a reference indicating alocation at which the task is to be accomplished. This may be a set ofgeographic coordinates or, more typically, a name of a business or otherlocation. To illustrate, if the task descriptor is a text message suchas “PICK UP MILK”, an appropriate reference might be “GROCERY STORE”.

FIG. 2 illustrates an exemplary situation where a vehicle 100 includes adigital system 5. Vehicle 100 has reached a location 102 which islocated a distance “R” from a GROCERY STORE 104. Assuming that a userhas previously stored a “PICK UP MILK” task with a reference to theGROCERY STORE as described above, the user will be alerted to “PICK UPMILK” in accordance with the present invention. The manner in which thisis accomplished is discussed further below.

After entering the task description in the database, the user willtransport mobile computer system 20 such that it is able to access thedatabase 10 (either because database 10 is contained within mobilecomputer system 20, for example, within Mem 24 or as a PC card or othercomputer readable storage medium, or because the units are linked via awireless communications link which may be routed through a cellulartelephone or modem system and/or the Internet) and is further able toreceive position information from location determination unit 30. Often,mobile computer system 20 will be a PDA and database 10 will either bestored within internal memory (e.g., Mem 24) or within a memory unit ona PC Card or other device attached to the PDA. In such cases, the PDAmay also include location determination unit 30. In other cases, the PDAmay connect to a docking port or other coupling arrangement within avehicle. In these cases, location determination unit 30 may operate as aGPS server within the vehicle as discussed above. Of course, mobilecomputer system 20 itself may be an integrated unit within the vehicle,in which case a memory component such as a PC Card or CD ROM on whichdatabase 10 is stored may be the only unit transported by the user. Thememory component would be provided to an appropriate device (for examplea PC Card port or CD ROM drive), thus making database 10 accessible bymobile computer system 20. Further, database 10 may be maintained on theuser's home or business computer system and may be accessed by mobilecomputer system 20 via a wireless communication link. In some cases, thecommunication link may be a cellular telephone link. Additionally, thecommunication link may route messages between mobile computer system 20and database 10 via the Internet using techniques well known in the art.Although such a link has not been shown in the Figure in order not toobscure the drawing, it will be appreciated that such a communicationlink would allow database 10 to be updated by more that one user atvarious times.

At some point, location determination unit 30 will receive and processGPS signals in the manner described above and will provide geographiclocation coordinates to mobile computer system 20 via interface 38.These geographic location coordinates will correspond to the geographiclocation of antenna 32, however, it is assumed that mobile computersystem 20 is in close enough proximity to antenna 32 such that thelocation of antenna 32 is substantially the same as the location ofmobile computer system 20. This condition will be satisfied, forexample, if mobile computer system 20 is transported within the samevehicle as that on which antenna 32 is located. Antenna 32 may be apatch antenna or other antenna suitable for mounting on a vehicle andcapable of receiving GPS signals transmitted by GPS satellites orpseudolites.

Once mobile computer system 20 has received the above-mentionedgeographic location coordinates (or other positioning information)provided by location determination unit 30, microprocessor 21 will usethis information to index database 10. Recall that database 10 containsa task description with an associated location reference (e.g., “GROCERYSTORE”). The location reference will have an associated geocode, i.e.,an associated set of geographic coordinates. This geocode is establishedat an earlier time, for example, by storing the location coordinates ofthe grocery store in the database 10 during an earlier trip to thestore, and is associated with the location reference that goes with thetask description. Thus, database 10 is a geocoded database that containstask descriptions with associated geocodes. Each time a task descriptionis entered and associated with a location reference, a geocode(corresponding to the location reference) is automatically associatedwith the task description.

Now, microprocessor 21 uses current positioning information provided bylocation determination unit 30 to index database 10 and retrieve taskdescriptions having associated geocodes which are close in proximity(e.g., within a city block radius) to the current geographic location ofmobile computer 20. In this way, a user can be alerted to a previouslyentered task based on the user's current position. To continue thegrocery store example, if mobile computer system 20 receives currentpositioning information from location determination unit 30 whichindicates that mobile computer system 20 (i.e., the user) is within apredetermined range “R” (e.g., 100-1600 meters) of the grocery store,the “PICK UP MILK” task description will be retrieved from database 10.This task description (which may also have an associated audio alarm ormessage) can be visually and/or audibly displayed over display 26 toalert the user that he or she is in close proximity to the grocery storeand should go pick up some milk. This feature can be enhanced bydisplaying a map (using information stored in Mem 24 or database 10)showing the user's current position (based on the location informationprovided by location determination unit 30) and the location of thegrocery store (using the geocode information associated with the storedtask description or location reference), thus allowing the user tonavigate a route to the grocery store.

In the above description, the database 10 is a database programmed bythe mobile computer system 20 user. However, database 10 may be providedas a unit by a commercial vendor. For example, database 10 may be soldas an “Electronic Yellow Pages” on CD ROM or other computer readableformat for use by a variety of mobile computer systems 20. In suchcases, database 10 may be an Internet Web Page or other resource.Regardless of its physical (or virtual) configuration, database 10includes geocoded references for a variety of business establishmentsand other locations (such as historical points of interest, stadiums,theaters, etc.) and is accessible by calendaring, scheduling and/orother application programs running on mobile computer system 20.

Alternatively, database 10 may originate as a commercially purchasedunit as described above and may be customized by a user through use. Forexample, database 10 may have an associated application program which“learns” a user's commute and purchasing habits, for example, byanalyzing electronic checkbook and/or other electronic account recordsand associating those entries with commute patterns derived fromposition information provided by location determination unit 30. Such adatabase could be used to prompt a user to make regular purchases (e.g.,milk) or deliveries when mobile computer system 10 is in an appropriategeographic location without requiring the user to enter a specific taskdescription.

Such a geocoded database would also be useful for a user who is new to ageographic area. For example, the user could purchase a database 10 fora particular city of interest (for example, shortly after moving to thecity) and use the database to locate stores, service providers, or otherlocations of interest. To illustrate, suppose the user has justpurchased a database 10 for ANY CITY and wants to locate the nearesthardware store (to buy items for his or her new home). By providing themobile computer system 20 with current positioning information fromlocation determination unit 30 and entering a search query via userinterface 25 seeking the location of the nearest hardware store,microprocessor 21 could access database 10 based on the positioninginformation and retrieve and display a list of hardware stores havinggeocodes which show the stores to be within a predetermined range (say amile or so) of the users current location. Upon selecting one of thestores from the list, a map (also stored on the media containingdatabase 10) could be visually displayed showing the user's presentlocation and the relative location of the hardware store.

In yet another embodiment, locations for anticipated vehicle stops for avehicle containing digital system 5 (or elements thereof when database10 is a remote unit) can be entered in database 10 each day and/orperiodically using user interface 25 and can also be entered on-the-flyby use of wireless communications as discussed above. Such an embodimentmay find use, for example, in a package pick-up/delivery system oranother system where such information is useful. As the vehiclecontaining digital system 5 follows a course, for example to allow forpackage pick-up/delivery, mobile computer system 10 accesses database 10to determine upcoming pick-up/drop-off points. This information can beaccessed based on an order of priority or, preferably, based on thelocation of the vehicle, as described above. In either case, thelocation of upcoming pick-up/drop-off points can be displayed visuallyand/or audibly on display 26. In addition, the present location of thevehicle can be displayed using location information provided by locationdetermination unit 30. Such information may be displayed as highlightedmarkers of a map or as a textual and/or graphical list. For this andother embodiments, e.g., where real-time traffic information is provided(either to a user or directly to mobile computer system 20, for example,via wireless transmissions), such a system may allow a user to determineand navigate a “best route” to the next pick-up/drop-off point.

Although the methods and apparatus of the present invention have beendescribed with reference to GPS satellites, it will be appreciated thatthe teachings are equally applicable to positioning systems whichutilize pseudolites or a combination of satellites and pseudolites.Pseudolites are ground based transmitters which broadcast a PN code(similar to a GPS signal) modulated on an L-band carrier signal,generally synchronized with GPS time. Each transmitter may be assigned aunique PN code so as to permit identification by a remote receiver.Pseudolites are useful in situations where GPS signals from an orbitingsatellite might be unavailable, such as tunnels, mines, buildings orother enclosed areas. The term “satellite”, as used herein, is intendedto include pseudolite or equivalents of pseudolites, and the term GPSsignals, as used herein, is intended to include GPS-like signals frompseudolites or equivalents of pseudolites.

It will be further appreciated that the methods and apparatus of thepresent invention are equally applicable for use with the GLONASS andother satellite-based positioning systems. The GLONASS system differsfrom the GPS system in that the emissions from different satellites aredifferentiated from one another by utilizing slightly different carrierfrequencies, rather than utilizing different pseudorandom codes. In thissituation, substantially all the circuitry and algorithms describedabove are applicable, however, a receiver need only store a single PNcode for use during receive operations.

Thus, a position based personal digital assistant has been described. Inthe foregoing specification, the present invention has been describedwith reference to specific exemplary embodiments thereof. It will,however, be evident that various modifications and changes may be madethereto without departing from the spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

What is claimed is:
 1. A computer assisted method of scheduling tasks,comprising the steps of: storing a task description in a database, saiddatabase being accessible by a mobile computer system; receiving at saidmobile computer system positioning information corresponding to thegeographic location of said mobile computer system; and indexing saiddatabase based on said positioning information so as to retrieve saidtask description when said position information indicates that saidmobile computer system is in a geographic location that is within aselected range of a location at which a task associated with said taskdescription may be performed.
 2. The computer assisted method of claim 1wherein said database is resident in said mobile computer system.
 3. Thecomputer assisted method of claim 1 wherein said database is accessiblevia the Internet.
 4. The computer assisted method of claim 1 whereinsaid task description includes a geocode, said geocode corresponding tosaid geographic location.
 5. The computer assisted method of claim 4wherein said task description further includes a textual message andsaid step of storing a task description comprises the steps of: enteringsaid textual message at a user terminal associated with said database;associating said textual message with said geocode to produce said taskdescription; and saving said task description in said database.
 6. Thecomputer assisted method of claim 5 wherein said positioning informationis received from one or more sources of pseudorandom sequence signalscontaining information indicative of the location of said one or moresources.
 7. The computer assisted method of claim 6 wherein at least oneof said sources is a Global Positioning System (GPS) satellite.
 8. Thecomputer assisted method of claim 6 wherein one of said sources is apseudolite.
 9. The computer assisted method of claim 6 wherein one ofsaid sources is a GLONASS satellite.
 10. The computer assisted method ofclaim 5 wherein said positioning information is received from a GPSreceiver.
 11. The computer assisted method of claim 5 wherein said stepof receiving positioning information comprises: collecting positioningsignals at an antenna associated with said mobile computer system;downconverting said positioning signals from an RF frequency to an IFfrequency to generate downconverting positioning signals; and extractingfrom said downconverting positioning signals said positioninginformation.
 12. The computer assisted method of claim 11 wherein saidpositioning information comprises a latitude and a longitude.
 13. Thecomputer assisted method of claim 12 further comprising the step ofalerting a user that said mobile computer system is in said geographiclocation after said step of indexing.
 14. The computer assisted methodof claim 13 wherein said step of alerting comprises playing out a voicemessage through a voice synthesizer associated with said mobile computersystem.
 15. The computer assisted method of claim 13 wherein said stepof alerting comprises displaying an alert message on a displayassociated with said mobile computer system.
 16. The computer assistedmethod of claim 13 wherein said mobile computer system is integrated ina vehicle.
 17. The computer assisted method of claim 16 wherein saidstep of alerting comprises playing out a voice message through an audiosystem associated with said vehicle.
 18. The computer assisted method ofclaim 16 wherein said step of alerting comprises displaying an alertmessage on a graphical display system associated with said vehicle. 19.The computer assisted method of claim 18 wherein said graphical displaysystem includes a heads up display and said alert message is displayedon said heads up display.
 20. The computer assisted method of claim 13wherein said step of alerting comprises displaying said textual messageon a display associated with said mobile computer system.
 21. A computerassisted method of using a geocoded database, comprising the steps of:transporting a mobile computer system to a first location having firstgeographic coordinates at a first time; receiving and processing at saidmobile computer system a first set of RF signals including pseudorandomsequences containing information indicative of the location of a sourceof said first set of RF signals to derive said first geographiccoordinates; associating said first geographic coordinates with adescriptor indicative of said first location in a database so as to forma geocoded entry in said database; and associating a task to beaccomplished at said first location with said geocoded entry in saiddatabase.
 22. The computer assisted method of claim 21 furthercomprising the steps of: transporting said mobile computer system to asecond location having second geographic coordinates at a second time;receiving and processing at said mobile computer system a second set ofRF signals including pseudorandom sequences containing informationindicative of the location of a source of said second set of RF signalsto derive said second geographic coordinates; analyzing said secondgeographic coordinates to determine whether said second location iswithin a predetermined range of said first location; and alerting a userof said mobile computer system of said task if said second location iswithin said predetermined range of said first location, otherwise notalerting said user of said task.
 23. The computer assisted method ofclaim 22 wherein said step of alerting comprises displaying an alertmessage on a display associated with said mobile computer system. 24.The computer assisted method of claim 23 wherein said alert messagecomprises a text message descriptive of said task and said step ofdisplaying comprises scrolling said text message on said display. 25.The computer assisted method of claim 22 wherein said step of alertingcomprises playing back a voice message descriptive of said task throughvoice synthesizing means associated with said mobile computer system.26. The computer assisted method of claim 25 wherein said voicesynthesizing means includes a vehicle audio system.
 27. A mobilecomputer system, comprising: a location determination unit configured toreceive and process RF signals including pseudorandom sequencesindicative of the location of a source of said RF signals to derive aset of location coordinates corresponding to the location of said mobilecomputer system; a database coupled to said location determination unitincluding location coordinates indicative of a location of interest andone or more task descriptors associated with said location of interest;and a database interface configured to access said database according tothe location of said mobile computer system.
 28. A mobile computersystem as in claim 27 wherein said database is stored on a computerreadable media.
 29. A mobile computer system as in claim 28 wherein saidcomputer readable media is a disk.
 30. A mobile computer system as inclaim 28 wherein said computer readable media is a CDROM.
 31. A mobilecomputer system as in claim 28 wherein said computer readable media isan EPROM.
 32. A mobile computer system as in claim 27 wherein said taskdescriptor comprises a text message.
 33. A mobile computer system as inclaim 27 wherein said task descriptor comprises a voice message.
 34. Amobile computer system as in claim 27 wherein said locationdetermination unit comprises a GPS server configured to provide saidlocation coordinates to said database interface across a computer businterconnecting said GPS server and said database interface.
 35. Amobile computer system as in claim 34 wherein said database interfacecomprises a microprocessor configured to access said database.
 36. Amobile computer system as in claim 35 wherein said mobile computersystem is integrated in a vehicle.